Don't cause an exception during configuration file building if matplotlib is installed, but not Sphinx.
Don't cause an exception during configuration file building if matplotlib is installed, but not Sphinx.

larrybradley/astropy,AustereCuriosity/astropy,funbaker/astropy,StuartLittlefair/astropy,saimn/astropy,pllim/astropy,AustereCuriosity/astropy,larrybradley/astropy,DougBurke/astropy,astropy/astropy,astropy/astropy,DougBurke/astropy,astropy/astropy,aleksandr-bakanov/astropy,saimn/astropy,stargaser/astropy,joergdietrich/astropy,lpsinger/astropy,tbabej/astropy,lpsinger/astropy,mhvk/astropy,StuartLittlefair/astropy,AustereCuriosity/astropy,lpsinger/astropy,kelle/astropy,funbaker/astropy,dhomeier/astropy,kelle/astropy,aleksandr-bakanov/astropy,dhomeier/astropy,mhvk/astropy,joergdietrich/astropy,aleksandr-bakanov/astropy,bsipocz/astropy,dhomeier/astropy,tbabej/astropy,bsipocz/astropy,saimn/astropy,stargaser/astropy,saimn/astropy,aleksandr-bakanov/astropy,joergdietrich/astropy,larrybradley/astropy,mhvk/astropy,joergdietrich/astropy,MSeifert04/astropy,pllim/astropy,mhvk/astropy,larrybradley/astropy,tbabej/astropy,StuartLittlefair/astropy,stargaser/astropy,stargaser/astropy,MSeifert04/astropy,joergdietrich/astropy,bsipocz/astropy,AustereCuriosity/astropy,StuartLittlefair/astropy,tbabej/astropy,funbaker/astropy,astropy/astropy,StuartLittlefair/astropy,funbaker/astropy,pllim/astropy,bsipocz/astropy,mhvk/astropy,AustereCuriosity/astropy,DougBurke/astropy,lpsinger/astropy,larrybradley/astropy,dhomeier/astropy,lpsinger/astropy,kelle/astropy,MSeifert04/astropy,kelle/astropy,saimn/astropy,kelle/astropy,pllim/astropy,MSeifert04/astropy,astropy/astropy,pllim/astropy,tbabej/astropy,dhomeier/astropy,DougBurke/astropy